The present invention relates to an improved process for the preparation of ethyl-3-{(5xe2x80x2-methylisoxazole-3xe2x80x2-carbonyl)-L-Valxcexa8(COCH2)-L-(4-F-Phe)-L-((S)-Pyrrol-Ala)}-E-propanoate, (also referred to as AG7088), its analogs and of pharmaceutically acceptable salts thereof. The present invention also includes a novel group of key intermediate compounds to be used in the above process.
Picornaviruses are a family of tiny non-enveloped positive-stranded RNA-containing viruses that infect humans and other animals. These viruses include the human rhinoviruses, human polioviruses, human coxsackieviruses, human echoviruses, human and bovine enteroviruses, encephalomyocarditis viruses, meningitis viruses, foot and mouth viruses, hepatitis A virus, and others. The human rhinoviruses are a major cause of the common cold.
Proteolytic 3C enzymes are required for the natural maturation of the picornaviruses. Thus, inhibiting the activity of these proteolytic 3C enzymes should represent an important and useful approach for the treatment and cure of viral infections of this nature, including the common cold.
Some small-molecule inhibitors of the enzymatic activity of picornaviral 3C protease (i.e., antipicornaviral compounds) have been recently discovered. See, for example: U.S. patent application Ser. No. 08/850,398, filed May 2, 1997, by Webber et al.; U.S. patent application Ser. No. 08/991,282, filed Dec. 16, 1997, by Dragovich et al.; and U.S. patent application Ser. No. 08/991,739, filed Dec. 16, 1997, by Webber et al. These U.S. patent applications, the disclosures of which are incorporated herein by reference, describe certain antipicornaviral compounds and methods for their synthesis.
More recently, an especially potent group of antipicornaviral agents have been discovered as set forth in U.S. patent application Ser. No. 60/098,354, (the ""354 application) filed Aug. 28, 1998, by Dragovich et al., which is herein incorporated by reference. This application discloses, inter alias, a group of antipicornaviral agents of general formula I. A particularly promising compound, AG7088, falling within the scope of this group, exhibits excellent antiviral properties against a plethora of Rhinoviral serotypes and is currently in human clinical trials. The ""354 application also discloses methods and intermediates useful for synthesizing these compounds. For example, General Method V therein discloses a general method for synthesizing the compounds of formula I involving subjecting a carboxylic acid of general formula BB to an amide-forming reaction with an amine of general formula P to provide a final product CC, as shown below. 
The ""354 application further discloses methods for synthesizing the intermediates of general formulae BB and P, and teaches methods for carrying out the amide-forming reaction referred to above. Thus, the ""354 application teaches suitable methods for synthesizing the compounds of general formula I from a carboxylic acid BB (within the scope of the compounds of general formula II referred to below) and the compounds of general formula P (the same as the compounds of general formula III referred to below.) Similarly, two recent publications by Dragovich et al. disclose antipicornavirus agents and suitable synthetic methods for their synthesis. See Structure-Based Design, Synthesis, and Biological Evaluation of Irreversable Human Rhinovirus 3C Proteases Inhibitors. 3. StructureActivity Studies of Ketomethylene-Containing Peptidonimietics, Dragovich et al., Journal of Medicinal Chemistry, ASAP, 1999; and Structure-Based Design, Synthesis, and Biological Evaluation of Irreversable Human Rhinovirus 3C Proteases Inhibitors. 4. Incorporation of P1 Lactam Moieties as L-Glutamine Replacements, Dragovich et al., Journal of Medicinal Chemistry, ASAP, 1999. These aforementioned articles are herein incorporated by reference in their entirety.
However, there is still a desire to discover improved, more efficient, processes and novel intermediates for use in the syntheses of the compounds of the group of antipicornaviral agents. In particular, there is a need for improved methods for synthesizing the compounds of general formulae II and III.
The present invention relates to the discovery of a cost effective and efficient process for the preparation of the antipicornaviral agents of formula I, such as compound AG7088, as well as intermediates which are useful in that synthesis.
The antipicornaviral agents of formula I comprise: 
wherein
R1 is H, F, an alkyl group, OH, SH, or an O-alkyl group;
R2 and R3 are each independently H; 
where n is an integer from 0 to 5, A1 is CH or N, A2 and each A3 are independently selected from C(R41)(R41), N(R41), S, S(O), S(O)2,and O and A4 is NH or NR41, where each R4l is independently H or lower alkyl, provided that no more than two heteroatoms occur consecutively in the above-depicted ring formed by A1, A2, (A3)n, A4 and Cxe2x95x90O, and at least one of R2 and R3 is 
R4 is 
R5 and R6 are each independently H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group;
R7 and R8 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94OR17, xe2x80x94SR17, xe2x80x94NR17R18, xe2x80x94NR19NR17R18, or xe2x80x94NR17OR18, where R17, R18, and R19 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, or an acyl group, provided that at least one of R7 and R8 is an alkyl group, an aryl group, a heteroaryl group, xe2x80x94OR17, xe2x80x94SR17, xe2x80x94NR17R18, xe2x80x94NR19NR17R18, or xe2x80x94NR17OR18; R9 is a five-membered heterocycle having from one to three heteroatoms selected from O, N, and S; and
Z and Z1 are each independently H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94C(O)R21, xe2x80x94CO2R21, CN, xe2x80x94C(O)NR21R22, xe2x80x94C(O)NR21OR22, xe2x80x94C(S)R21, xe2x80x94C(S)NR21R22, xe2x80x94NO2, xe2x80x94SOR21, xe2x80x94SO2R21, xe2x80x94SO21NR21R22, xe2x80x94SO(NR21)(OR22), xe2x80x94SONR21, xe2x80x94SO3R21, xe2x80x94PO(OR21)2 xe2x80x94PO(R21)(R22), xe2x80x94PO(NR2lR22)(OR23), xe2x80x94PO(NR21R22)(NR23R24), xe2x80x94C(O)NR21NR22R23, or xe2x80x94C(S)NR21NR22R23, where R21, R22, R23, and R24 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, an acyl group, or a thioacyl group, or where any of two of R21,R22, R23, and R24, together with the atom(s) to which they are bonded, form a heterocycloalkyl group, provided that Z and Z1 are not both H;
or Z1 and R1, together with the atoms to which they are bonded, form a cycloalkyl or heterocycloalkyl group, where Z1 and R1 are as defined above except for moieties that cannot form the cycloalkyl or heterocycloalkyl group;
or Z and Z1, together with the atoms to which they are bonded, form a cycloalkyl or heterocycloalkyl group, where Z and Z1 are as defined above except for moieties that cannot form the cycloalkyl or heterocycloalkyl group.
As discussed below, these antipicornaviral agents of formula I may be synthesized by subjecting a compound of general formula II together with a compound of general formula III to a suitable amide-forming reaction. The process of the present invention, not only reduces the number of steps required to synthesize the compounds of formula III, but more importantly, it also employs less expensive starting materials and reagents.
These objects, advantages and features of the present invention will be more fully understood and appreciated by reference to the written specification.
As used in the present application, the following definitions apply:
In accordance with a convention used in the art, 
is used in structural formulas herein to depict the bond that is the point of attachment of the moiety or substituent to the core or backbone structure.
Where chiral carbons are included in chemical structures, unless a particular orientation is depicted, both sterioisomeric forms are intended to be encompassed.
An xe2x80x9calkyl groupxe2x80x9d is intended to mean a straight or branched chain monovalent radical of saturated and/or unsaturated carbon atoms and hydrogen atoms, such as methyl (Me), ethyl (Et), propyl, isopropyl, butyl (Bu), isobutyl, t-butyl (t-Bu), ethenyl, pentenyl, butenyl, propenyl, ethynyl, butynyl, propynyl, pentynyl, hexynyl, and the like, which may be unsubstituted (i.e., containing only carbon and hydrogen) or substituted by one or more suitable sustituents as defined below (e.g., one or more halogens, such as F, Cl, Br, or I, with F and Cl being prefered). A xe2x80x9clower alkyl groupxe2x80x9d is intended to mean an alkyl group having from 1 to 4 carbon atoms in its chain.
A xe2x80x9ccycloalkyl groupxe2x80x9d is intended to mean a non-aromatic monovalent monocyclic, bicyclic, or tricyclic radical containing 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 carbon ring atoms, each of which may be saturated or unsaturated, and which may be unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more heterocycloalkyl groups, aryl groups, or heteroaryl groups, which themselves may be unsubstituted or substituted by one or more substituents. Illustrative examples of cycloalkyl groups include the following moieties: 
A xe2x80x9cheterocycloalky groupxe2x80x9d is intended to mean a non-aromatic monovalent monocyclic, bicyclic, or tricyclic radical, which is saturated or unsaturated, containing 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 ring atoms, which includes 1, 2, 3, 4, or 5 heteroatoms selected nitrogen, oxygen, and sulfur, where the radical is unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more cycloalkyl groups, aryl groups, or heteroaryl groups, which themselves may be unsubstituted or substituted by one or more suitable substituents. Illustrative examples of heterocycloalkyl groups include the following moieties: 
An xe2x80x9caryl groupxe2x80x9d is intended to mean an aromatic monovalent monocyclic, bicyclic, or tricyclic radical containing 6, 10, 14 or 18 carbon ring atoms, which may be unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more cycloalkyl groups, heterocycloalkyl groups, or heteroaryl groups, which themselves may be unsubstituted or substituted by one or more suitable substituents. Illustrative examples of aryl groups include the following moieties: 
A xe2x80x9cheteroaryl groupxe2x80x9d is intended to mean an aromatic monovalent monocyclic, bicyclic, or tricyclic radical containing 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 ring atoms, including 1, 2, 3, 4, or 5 heteroatoms selected from nitrogen, oxygen, and sulfur, which may be unsubstituted or substituted by one or more suitable substituents as defined below, and to which may be fused one or more cycloalkyl groups, heterocycloalkyl groups, or aryl groups, which themselves may be unsubstituted or substituted by one or more suitable substituents. Illustrative examples of heteroaryl groups include the following moieties: 
A xe2x80x9cheterocyclexe2x80x9d is intended to mean a heteroaryl or heterocycloalkyl group (each of which, as defined above, are optionally substituted).
An xe2x80x9cacyl groupxe2x80x9d is intended to mean a xe2x80x94C(O)xe2x80x94R radical, where R is a substituent as defined below.
A xe2x80x9cthioacyl groupxe2x80x9d is intended to mean a xe2x80x94C(S)xe2x80x94R radical, where R is a substituent as defined below.
A xe2x80x9csulfonyl groupxe2x80x9d is intended to mean a xe2x80x94SO2R radical, where R is a substituent as defined below.
A xe2x80x9chydroxy groupxe2x80x9d is intended to mean the radical xe2x80x94OH.
An xe2x80x9camino groupxe2x80x9d is intended to mean the radical xe2x80x94NH2.
An xe2x80x9calkylamino groupxe2x80x9d is intended to mean the radical xe2x80x94NHRa, where Ra is an alkyl group.
A xe2x80x9cdialkylamino groupxe2x80x9d is intended to mean the radical xe2x80x94NRaRb, where Ra and Rb are each independently an alkyl group.
An xe2x80x9calkoxy groupxe2x80x9d is intended to mean the radical xe2x80x94ORa, where Ra is an alkyl group. Exemplary alkoxy groups include methoxy, ethoxy, propoxy, and the like.
An xe2x80x9calkoxycarbonyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)ORa, where Ra is an alkyl group.
An xe2x80x9calkylsulfonyl groupxe2x80x9d is intended to mean the radical xe2x80x94SO2Ra, where Ra is an alkyl group.
An xe2x80x9calkylaminocarbonyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)NHRa, where Ra is an alkyl group.
A xe2x80x9cdialkylaminocarbonyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)NRaRb, where Ra and Rb are each independently an alkyl group.
A xe2x80x9cmercapto groupxe2x80x9d is intended to mean the radical xe2x80x94SH.
An xe2x80x9calkylthio groupxe2x80x9d is intended to mean the radical xe2x80x94SRa, where Ra is an alkyl group.
A xe2x80x9ccarboxy groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)OH.
A xe2x80x9ccarbamoyl groupxe2x80x9d is intended to mean the radical xe2x80x94C(O)NH2.
An xe2x80x9caryloxy groupxe2x80x9d is intended to mean the radical xe2x80x94ORc, where Rc, is an aryl group.
A xe2x80x9cheteroaryloxy groupxe2x80x9d is intended to mean the radical xe2x80x94ORd, where Rd is a heteroaryl group.
An xe2x80x9carylthio groupxe2x80x9d is intended to mean the radical xe2x80x94SRc, where Rc is an aryl group.
A xe2x80x9cheteroarylthio groupxe2x80x9d is intended to mean the radical xe2x80x94SRd, where Rd is a heteroaryl group.
A xe2x80x9cleaving groupxe2x80x9d (Lv) is intended to mean any suitable group that will be displaced by a substitution reaction. One of ordinary skill in the art will know that any conjugate base of a strong acid can act as a leaving group. Illustrative examples of suitable leaving groups include, but are not limited to, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, alkyl chlorides, alkyl bromides, alkyl iodides, alkyl sulfonates, alkyl benzenesulfonates, alkyl p-toluenesulfonates, alkyl methanesulfonates, triflate, and any groups having a bisulfate, methyl sulfate, or sulfonate ion.
Typical protecting groups, reagents and solvents such as, but not limited to, those listed below in table 1 have the following abbreviations as used herein and in the claims. One skilled in the art would understand that the compounds listed within each group may be used interchangeably; for instance, a compound listed under xe2x80x9creagents and solventsxe2x80x9d may be used as a protecting group, and so on. Further, one skilled in the art would know other possible protecting groups, reagents and solvents; these are intended to be within the scope of this invention.
The term xe2x80x9csuitable organic moietyxe2x80x9d is intended to mean any organic moiety recognizable, such as by routine testing, to those skilled in the art as not adversely affecting the inhibitory activity of the inventive compounds. Illustrative examples of suitable organic moieties include, but are not limited to, hydroxyl groups, alkyl groups, oxo groups, cycloalkyl groups, heterocycloalkyl groups, aryl groups, heteroaryl groups, acyl groups, sulfonyl groups, mercapto groups, alkylthio groups, alkoxy groups, carboxy groups, amino groups, alkylamino groups, dialkylamino groups, carbamoyl groups, arylthio groups, heteroarylthio groups, and the like.
The term xe2x80x9csubstituentxe2x80x9d or xe2x80x9csuitable substituentxe2x80x9d is intended to mean any suitable substituent that may be recognized or selected, such as through routine testing, by those skilled in the art. Illustrative examples of suitable substituents include hydroxy groups, halogens, oxo groups, alkyl groups, acyl groups, sulfonyl groups, mercapto groups, alkylthio groups, alkyloxy groups, cycloalkyl groups, heterocycloalkyl groups, aryl groups, heteroaryl groups, carboxy groups, amino groups, alkylamino groups, dialkylamino groups, carbamoyl groups, aryloxy groups, heteroaryloxy groups, arylthio groups, heteroarylthio groups, and the like.
The term xe2x80x9coptionally substitutedxe2x80x9d is intended to expressly indicate that the specified group is unsubstituted or substituted by one or more suitable substituents, unless the optional substituents are expressly specified, in which case the term indicates that the group is unsubstituted or substituted with the specified substituents. As defined above, various groups may be unsubstituted or substituted (i.e., they are optionally substituted) unless indicated otherwise herein (e.g., by indicating that the specified group is unsubstituted).
A xe2x80x9cprodrugxe2x80x9d is intended to mean a compound that is converted under physiological conditions or by solvolysis or metabolically to a specified compound that is pharmaceutically active.
A xe2x80x9cpharmaceutically active metabolitexe2x80x9d is intended to mean a pharmacologically active product produced through metabolism in the body of a specified compound.
A xe2x80x9csolvatexe2x80x9d is intended to mean a pharmaceutically acceptable solvate form of a specified compound that retains the biological effectiveness of such compound. Examples of solvates include compounds of the invention in combination with water, isopropanol, ethanol, methanol, DMSO, ethyl acetate, acetic acid, or ethanolamine.
A xe2x80x9cpharmaceutically acceptable saltxe2x80x9d is intended to mean a salt that retains the biological effectiveness of the free acids and bases of the specified compound and that is not biologically or otherwise undesirable. Examples of pharmaceutically acceptable salts include sulfates, pyrosulfates, bisulfates, sulfites, bisulfites, phosphates, monohydrogenphosphates, dihydrogenphosphates, metaphosphates, pyrophaosphates, chlorides, bromides, iodides, acetates, propionates, decanoates, caprylates, acrylates, formates, isobutyrates, caproates, heptanoates, propiolates, oxalates, malonates, succinates, suberates, sebacates, fumarates, maleates, butyne-1,4-dioates, hexyne-1,6-dioates, benzoates, chlorobenzoates, methylbenzoates, dinitrobenzoates, hydroxybenzoates, methoxybenzoates, phthalates, sulfonates, xylenesulfonates, phylacetates, phenylpropionates, phylbutyrates, citrates, lactates, xcex3-hydroxybutyrates, glycollates, tartrates, methane-sulfonates, propanesulfonates, naphthalene-1-sulfonates, naphthalene-2-sulfonates, and mandelates.
The present invention further provides synthetic methods that are comprised of one of the synthetic steps set forth in the present disclosure. A synthetic method is comprised of a synthetic step when the synthetic step is at least part of the final synthetic method. In such a fashion, the synthetic method can be only the synthetic step or have additional synthetic steps that may be associated with it. Such a synthetic method can have a few additional synthetic steps or can have numerous additional synthetic steps.
If the antipicornaviral agent of formula I formed from the process of the present invention is a base, a desired salt may be prepared by any suitable method known to the art, including treatment of the free base with an inorganic acid, such as hydrochloric acid; hydrobromic acid; sulfuric acid; nitric acid; phosphoric acid; and the like, or with an organic acid, such as acetic acid; maleic acid; succinic acid; mandelic acid; fumaric acid; malonic acid; pyruvic acid; oxalic acid; glycolic acid; salicylic acid; pyranosidyl acid, such as glucuronic acid or galacturonic acid; alpha-hydroxy acid, such as citric acid or tartaric acid; amino acid, such as aspartic acid or glutamic acid; aromatic acid, such as benzoic acid or cinnamic acid; sulfonic acid, such as p-toluenesulfonic acid or ethanesulfonic acid; or the like.
If the antipicornaviral agent of formula I formed from the process of the present invention is an acid, a desired salt may be prepared by any suitable method known to the art, including treatment of the free acid with an inorganic or organic base, such as an amine (primary, secondary, or tertiary); an alkali metal or alkaline earth metal hydroxide; or the like. Illustrative examples of suitable salts include organic salts derived from amino acids such as glycine and arginine; ammonia; primary, secondary, and tertiary amines; and cyclic amines, such as piperidine, morpholine, and piperazine; as well as inorganic salts derived from sodium, calcium, potassium, magnesium, manganese, iron, copper, zinc, aluminum, and lithium.
In the case of compounds, salts, or solvates that are solids, it is understood by those skilled in the art that the compounds of formula I and the intermediates used in the process of the present invention, salts, and solvates thereof, may exist in different crystal forms, all of which are intended to be within the scope of the present invention and specified formulas.
The antipicornaviral agents of formula I, and the intermediates used in the process of the present invention, may exist as single stereoisomers, racemates, and/or mixtures of enantiometers and/or diastereomers. All such single stereoisomers, racemates, and mixtures thereof are intended to be within the broad scope of the present invention. Preferably, however, the intermediate compounds used in the process of the present invention are used in optically pure form.
As generally understood by those skilled in the art, an optically pure compound is one that is enantiomerically pure. As used herein, the term xe2x80x9coptically purexe2x80x9d is intended to mean a compound comprising at least a sufficient amount of a single enantiomer to yield a compound having the desired pharmacological activity. Preferably, xe2x80x9coptically purexe2x80x9d is intended to mean a compound that comprises at least 90% of a single isomer (80% enantiomeric excess (hereinafter xe2x80x9ce.e.xe2x80x9d)), more preferably at least 95% (90% e.e.), even more preferably at least 97.5% (95% e.e.), and most preferably at least 99% (98% e.e.) Preferably, the antipicornaviral agents of formula I formed from the process of the present invention are optically pure.
The present invention relates to a process of preparing antipicornaviral agents of formula I: 
wherein
R1 is H, F, an alkyl group, OH, SH, or an O-alkyl group;
R2 and R3 are each independently H; 
where n is an integer from 0 to 5, A1 is CH or N, A2 and each A3 are independently selected from C(R41)(R41), N(R41), S, S(O), S(O)2, and O, and A4 is NH or NR41, where each R41, is independently H or lower alkyl, provided that no more than two heteroatoms occur consecutively in the above-depicted ring formed by A1, A2, (A3),n, A4 and Cxe2x95x90O, and at least one of R2 and R3 is 
R4 is 
R5 and R6 are each independently H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, or a heteroaryl group;
R7 and R8 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94OR17, xe2x80x94SR17, xe2x80x94NR17R18, xe2x80x94NR19NR17R18, or xe2x80x94NR17OR18, where R17, R,18, and Rl19 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, or an acyl group, provided that at least one of R7 and R8 is an alkyl group, an aryl group, a heteroaryl group, xe2x80x94OR17, xe2x80x94SR17, xe2x80x94NR17R18xe2x80x94NR19NR17R18, or xe2x80x94NR17OR18; R9 is a five-membered heterocycle having from one to three heteroatoms selected from O, N, and S; and
Z and Z1 are each independently H, F, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, xe2x80x94C(O)R21, xe2x80x94CO2R21, CN, xe2x80x94C(O)NR21R22, xe2x80x94C(O)NR21OR22, xe2x80x94C(S)R21, xe2x80x94C(S)NR21R22, xe2x80x94NO2, xe2x80x94SOR21, xe2x80x94SO2R21, xe2x80x94SO2NR21R22, xe2x80x94SO(NR21)(OR22), xe2x80x94SONR21, xe2x80x94SO3,R21, xe2x80x94PO(OR21)2, xe2x80x94PO(R21)(R22), xe2x80x94PO(NR21R22)(OR23), xe2x80x94PO(NR21R22)(NR23R24), xe2x80x94C(O)NR21NR22R23, or xe2x80x94C(S)NR21NR22R23, where R21, R22, R23, and R24 are each independently H, an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroaryl group, an acyl group, or a thioacyl group, or where any of two of R21, R22, R23, and R24, together with the atom(s) to which they are bonded, form a heterocycloalkyl group, provided that Z and Z1 are not both H;
or Z1 and R1, together with the atoms to which they are bonded, form a cycloalkyl or heterocycloalkyl group, where Z1 and R1 are as defined above except for moieties that cannot form the cycloalkyl or heterocycloalkyl group;
or Z and Z1, together with the atoms to which they are bonded, form a cycloalkyl or heterocycloalkyl group, where Z and Z1 are as defined above except for moieties that cannot form the cycloalkyl or heterocycloalkyl group.
The present invention discloses that a compound of formula I may be prepared by subjecting a compound of formula II and a compound of formula III to a amide-forming reaction: 
The amide-forming reaction may be achieved by any suitable method, reagents and reaction conditions. Preferably, any one of the methods disclosed in the ""354 application is utilized. For example, a compound of formula II may be reacted with a compound of formula III in the presence of HATU, DIPEA, CH3CN and H2O to yield desired compound of formula I. Any suitable purification method may be used to further purify the compound of formula I.
More preferably, the compound of formula I is prepared by an amide-forming reaction comprising the steps of:
(a) reacting the compound of formula II with a compound of formula IIIA in the presence of N-methylmorpholine to form a reaction mixture; and 
(b) adding a compound of formula Lv-X to the reaction mixture to form a compound of formula I, wherein X is any suitable halide.
Preferably, the method for preparing the compound of formula I utilizing the more preferable amide-forming reaction utilizes some or all of the reagents and reaction conditions disclosed below. Thus, preferably, the compound of formula II and the compound of formula IIIA in DMF are combined in any suitable container. The suitable container is preferably a single neck flask which is then covered with any suitable septum and covered with a temperature probe. Nitrogen gas is used to purge out the suitable container before N-methylmorpholine is added to the reaction mixture. More preferably, the N-methylmorpholine is added via a syringe in one single portion and the reaction mixture cooled to about between xe2x88x925xc2x0 C. and 5xc2x0 C. More preferably, the reaction mixture is cooled to about 0xc2x0 C. A solution of the compound of formula Lv-X is then added to the reaction mixture. More preferably, the solution of the compound of formula Lv-X is a solution of the compound of formula Lv-X in DMF. Even more preferably, the compound of formula Lv-X is CDMT. The solution of the compound of formula Lv-X is added to the reaction mixture by any suitable method so as to maintain the reaction mixture at a constant temperature. For example, the solution of the compound of formula Lv-X may be added to the reaction mixture dropwise utilizing a syringe. Upon completion of the addition of the solution of the compound of formula Lv-X, the reaction mixture is allowed to warm to about room temperature. The progress of the reaction may be followed by monitoring the disappearance of the compound of formula II by thin layer chromatography (hereinafter xe2x80x9cTLCxe2x80x9d). When the reaction is at least substantially complete, the compound of formula I may be precipitated out of solution to form a slurry by slowly adding water to the reaction mixture. The compound of formula I may then be removed from the slurry by any suitable means known to one of ordinary skill in the art. For example, the compound of formula I may be removed from the slurry by filtration. Any suitable purification method known to one of ordinary skill in the art may be used to purify the compound of formula I. More preferably, the compound of formula I is purified by recrystalization.
The present invention also discloses two alternate processes for the synthesis of the compound of formula III and acid addition salts thereof. Of these two routes, the second process is currently preferred because it offers greater cost-effectiveness at a commercial scale.
The first of these two processes is for the preparation of a compound of formula IV and its acid addition salts from a compound of formula V. 
One of ordinary skill will recognize that the compounds of formula IV are a subgenus to those of formula III.
The compound of formula V may be prepared from commercially available N-Boc L glutanic acid xcex3-benzyl ester. Any suitable method may be used to prepare the compound of formula V. Preferably, the method disclosed in U.S. patent application Ser. No. 08/991,739 is used. U.S. patent application Ser. No. 08/991,739 is herein incorporated by reference in its entirety.
The process of the present invention comprises the steps of:
(a) cyanomethylation of the compound of formula V using bis(trimethysily)amide and bromoacetonitrile to yield a compound of formula VI; 
(b) the reduction, cyclization, and deprotection of the compound of formula VI in that respective order to yield a compound of formula VII; and 
(c) the oxidation and olefination of the compound of formula VII by reacting the compound with a SO3-pyridine complex to yield a reaction mixture and reacting the reaction mixture with a phosphorane of formula VIII. 
According to the present invention, and as disclosed above, the preparation of the compound of formula V from N-Boc glutanic acid xcex3-benzyl ester may be carried out by any suitable method known in the art.
Further, the cyanomethylation of the compound of formula V may be carried out using any suitable method, reagents and reaction conditions. Preferably, the method disclosed below and the use of all or some of the reagents and reaction conditions are used. Thus, it is preferable, that the compound of formula V be added dropwise to a stirring solution of NaHMDS in THF at xe2x88x9270xc2x0 C. in a nitrogen atmosphere over a period of at least about 5 hours before being mixed with bromoacetonitrile.
This cyanomethylation of the compound of formula V using bis(trimethylsilyl)amide and bromoacetonitrile affords the compound of formula VI along with its epimer in a 5:1 ratio. However, the compound may be purified by any suitable method. Preferably, the compound of formula VI is purified by filtration and chromatography, followed by titration. Under these preferred conditions, a 60% overall yield of the compound of formula VI is attainable having  greater than 99% diastereomeric purity.
The three step reduction, cyclization, and deprotection reaction of step (b) to convert the compound of formula VI to the compound of formula VII may be carried out using any suitable reagents and reaction conditions. Preferably, the method disclosed below, using all or some of the reagents and reaction conditions are used. Therefore, preferably, the compound of formula VI is reduced by adding a solution of cobalt (II) chloride hexahydrate to a solution of the compound of formula VI in tetrahydrofuran in methanol. The resulting solution is cooled to about 0xc2x0 C. before sodium borohydride is added in portions over a period of at least about 7 hours. Then, p-toluensulfonic acid monohydrate is added to the solution of crude material in methanol and allowed to react for at least about 18 hours at an ambient temperature. After removal of the solvent, the residue is dissolved in ethyl acetate and washed. Any suitable washing agent may be used. More preferably, the washing agent is saturated sodium bicarbonate. The crude product is then charged with a solution of methanol in water. More preferably, a 2.5% methanol solution is used. The crude product may be removed from solution by any suitable method. For example, the crude product may be removed by filtration and the filtrate concentrated on a rotary evaporator. The product is then dissolved in ethyl acetate, dried, filtered and concentrated to the crude compound of formula VII. More preferably, the product is dried over MgSO4. The crude compound of formula VII may be further purified by any suitable purification process. More preferably, the crude compound of formula VII is purified through a titration process using 1:1 ethyl acetate and hexanes.
An overall yield of at least about 95% pure compound of formula VII is attainable if the preferred three step reduction, cyclization, and deprotection reaction disclosed above is used.
Any suitable method, reagents and reaction conditions may be used in the subsequent oxidation and olefination employing a SO3-pyridine complex and the phosphorane of formula VIII to yield the compound of formula IV. Preferably, the method disclosed below and all or some of the reagents and reaction conditions are used. Accordingly, preferably, triethylamine is added to a solution of the compound of formula VIII and methylsulfoxide. The resulting solution is cooled to about 5xc2x0 C., followed by the addition of a sulfur trioxide-pyridine complex. The reaction is stirred at about 5xc2x0 C. for at least about 15 minutes. After removing the source used to cool the solution to about 5xc2x0 C., the reaction is stirred for at least about an additional 1 hour. (Carboethoxymethylenetriphenyl)-phosphorane is then added and the reaction mixture stirred at ambient temperature for at least about 3 hours. Then, the reaction is quenched and extracted with ethyl acetate. More preferably, the reaction is quenched by the addition of saturated brine. The combined organic phases are then washed, dried, filtered and concentrated to afford crude compound of formula IV. More preferably, the combined organic phases are washed with saturated brine and dried over MgSO4.
The compound of formula IV may be purified by any suitable method. Preferably, chromatography purification and titration techniques are used. If the preferable purification technique is used, yields ranging from 55% to 60% are attainable.
The second process for preparing the compound of formula IV, and its acid addition salts, disclosed by the present invention comprises the steps of:
(a) the dianionic alkylation of a compound of formula IX using bromoacetonitrile to yield a compound of formula X; 
(b) hydrogenation of the compound of formula X to yield an amine of formula XI; 
(c) reacting the amine of formula XI with ET3N to yield a lactam ester of formula XII; 
(d) the reduction of the lactam ester of formula XII through a suitable reduction procedure to yield a compound of formula XIII; 
(e) the oxidation and olefination of the compound of formula XIII to yield a compound of formula XIV by reacting it with a compound of formula XV; and 
(f) converting the compound of formula XIV to the compound of formula IV.
Further, one of ordinary skill in the art will realize that the above disclosed method may be used to prepare the compound of formula XIV. Specifically, steps (a)-(e) disclose a process for preparing the compound of formula XIV.
The compound of formula IX may be prepared by any suitable method known in the art. For example, N-Boc L-(+)-glutamic acid dimethyl ester may be prepared from commercially available L-glutamic acid dimethyl ester hydrochloride or commercially available L-glutamic acid 5-methyl ester according to literature procedures. See for example, Shimamoto et al, J. Org. Chem. 1991, 56, 4167 and Duralski et al, Tetrahedron Lett. 1998, 30, 3585. These references are herein incorporated by reference in their entirety.
Preferably, the dianionic alkylation reaction is performed using the method and all or some of the reagents and reaction conditions disclosed below. Therefore, preferably, the compound of formula IX is first dissolved in THF to form a solution which is added dropwise to a stirring solution of LiHMDS at xe2x88x9278xc2x0 C. in an Argon atmosphere. The resulting mixture is then stirred at about xe2x88x9278xc2x0 C. for 2 hours before freshly distilled bromoacetonitrile is added dropwise over a period of 1 hour. The reaction mixture is stirred at about xe2x88x9278xc2x0 C. for additional 2 hours. The reaction is then quenched. More preferably, the reaction is quenched by adding 0.5 M HCl and H2O. The resulting aqueous layer is separated and is extracted further with methyl tert-butyl ether. The combined organic extract is washed, dried and filtered. More preferably, the organic extract is washed with saturated NaHCO3 and brine and dried over MgSO4. The solvent is evaporated under reduced pressure.
The compound of formula IX may be hydrogenated to the amine of formula XI by any suitable method known in the art. Preferably, the hydrogenation is performed in the presence of 5% Pd/C. More preferably, the hydrogenation reaction is performed in accordance with the method, using some or all of the reagents and reaction conditions disclosed below. According to this preferred hydrogenation method, the compound of formula IX is dissolved in HOAc and shaken with 5% Pd on C under H2 gas, at 50 psi pressure, for 3 days. The mixture is then filtered over celite. The filtrate may then be evaporated under reduced pressure and the residue repeatedly evaporated from methyl tert-butyl ether.
The reaction of the amine of formula XI with Et3N may be achieved using any suitable conditions. Preferably, the method and all or some of the reagents and reaction conditions disclosed below are used. Accordingly, preferably, the amine of formula XI is dissolved in 1:1 MeOH/THF, before Et3N is added to the solution. The resulting mixture is stirred at about 45xc2x0 C. for about 10 hours or until the starting material has disappeared. The presence of the starting material may be monitored by 1H NMR. After stripping off the solvent, methyl tert-butyl ether is added. The precipitate is then filtered. 0.5 M HCl is added to the filtrate diluted with H2O. After splitting the phases, the aqueous phase may be extracted with ethyl acetate. The combined organic phases are washed, dried, filtered and concentrated. More preferably, the combined organic phases are washed with brine and dried over MgSO4. The phases may be concentrated on a rotovapor. Flash chromatography furnishes the lactam ester of formula XII.
Any suitable reduction method may be used to convert the lactam ester of formula XII to the compound of formula XIII. Preferably, LiBH4 is used as the reducing agent. More preferably, the method, or any portion thereof, and any or all of the reagents and reaction conditions disclosed below are used. Thus, more preferably, LiBH4 is added to a stirring solution of the lactam ester of formula XII in THF. The LiBH4 is added in several portions at 0xc2x0 C. in an Argon atmosphere. The reaction mixture is stirred at 0xc2x0 C. for 10 minutes, before being allowed to warm to ambient temperature and stirred for an additional 2 hours. Then, the reaction is quenched. Even more preferably, the reaction is quenched by the dropwise addition of 0.5 M HCl while cooling using an ice bath. The solution is diluted with ethyl acetate and H2O. After splitting the phases, the aqueous phase may be extracted with ethyl acetate. The combined organic phases are washed, dried, filtered and concentrated. Even more preferably, the combined organic phases are washed with brine and dried over MgSO4. The phases may be concentrated on a rotovapor. Flash chromatography furnishes the compound of formula XII.
Any suitable oxidation and olefination method may be used to prepare the compound of formula XIV from the compound of formula XIII. Preferably, the method, or any part thereof, and all or some of the reagents and reaction conditions described below are used. Thus, in accordance with the present invention, benzoic acid, (carboethoxymethylenetriphenyl)phosphorane and DMSO are added to a solution of the compound of formula XIII in CH2Cl2. Dess-Martin periodinane is added to the solution in several portions, and the reaction mixture is then stirred for at least about 5 hours at ambient temperature until the compound of formula XIII substantially disappears. The presence of the compound of formula XIII may be monitored by 1H NMR. Saturated NaHCO3 solution is added before the mixture is stirred for 30 minutes to yield a precipitate. The precipitate is filtered prior to the organic phase of the filtrate being separated, washed, and concentrated to yield the crude compound of formula XIV. More preferably, the filtrate is washed with brine and concentrated on a rotovapor. Any suitable method may be used to purify the crude compound of formula XIV. More preferably, the crude compound of formula XIV is purified by flash chromatography, then dissolved in ethyl acetate. Excess hexanes are then added gradually to the stirring solution to yield a precipitated. The precipitate is filtered and dried to afford the compound of formula XIV. More preferably, the precipitate is dried in a vacuum oven for at least about 12 hours.